Dr Klein suggests that APACHE II scores measured at the time of hospital admission could be used to control for lead-time bias. We disagree. The assessment of illness severity in patients transferred to the MICU from other inpatient sites is subject to lead-time bias because some treatments administered prior to the transfer affect the physiological variables used to assess severity without improving the underlying disease processes. There is no reason to believe that the magnitude of these effects is systematically related to the APACHE II score on hospital admission.In this connection, it is worth noting that lead-time bias can affect patients admitted to the MICU from the emergency department as well as those transferred from other inpatient sites. Indeed, one goal of the APACHE III study is to examine the biases that arise because patients are variably stabilized in the emergency department before admission to the MICU.
Escarce JJ, Kelley MA. APACHE Scores-Reply. JAMA. 1991;265(8):978. doi:10.1001/jama.1991.03460080048029